DESCRIPTION: Middle childhood is an important developmental era marked by the child's entry into social systems outside the home and by emergence of long-term prediction of cognitive and socioemotional functioning later in life. Despite the theoretical and practical importance of middle childhood, little is known about the genetic and environmental origins of individual differences during this era or about their links with development before and after middle childhood. The purpose of the proposed 3-year continuation is to complete the investigators' longitudinal prospective study of 7-year-olds that combines family, adoption, and twin data to provide the most powerful possible design to investigate the origins of individual differences in middle childhood and their earlier and later developmental links. Testing 183 twin pairs at age 7 will complete the investigators' study of 624 adopted and nonadopted children and 435 twin pairs at 7 years who have been studied yearly during infancy and early childhood and whom will continue to be studied in adolescence and early adulthood. Genetic and environmental influences on behavior will be assessed employing multivariate maximum-likelihood, model-fitting analyses to test hypotheses of genetic and environmental influences on 7-year functioning and on the association between 7-year functioning and earlier and later developmental and environmental data obtained for these same children. The project's large sample, its multivariate and longitudinal approach, and its combined family, adoption, and twin design have made this a landmark study of behavioral development in middle childhood. The purpose of the present request is to capitalize on previous support in order to complete this unique study.